Distribution of CEO Ages The distribution of ages of CEOs is as follows:
$$
\begin{array}{ll}{\text { Age }} & {\text { Frequency }} \\ \hline 21-30 &\quad\quad { 1 } \\ {31-40} &\quad\quad {8} \\ {41-50} &\quad \quad{27} \\ {51-60} & \quad\quad{29} \\ {61-70} &\quad\quad {24} \\ {71-4 p} & \quad\quad{11}\end{array}
$$
If a CEO is selected at random, find the probability that his or her age is
a. Between 31 and 40
b. Under 31
c. Over 30 and under 51
d. Under 31 or over 60